Twisted-pair cable particularly in building wiring systems provides a transmission medium for communication of data or other signals at high speeds, with great reliability and for relatively low cost. It will be understood by those skilled in the art to which this invention pertains that the term "twisted-pair" cable refers to a plurality of electrically conducting wires housed within an insulative outer covering with each pair of wires carrying differential signals and twisted together to diminish extraneous noise or crosstalk which otherwise reduces the integrity of the signal. In addition, the term "building wire" refers to any twisted-pair conductors that have a sufficiently long length that would preclude other wiring types such as flat conductors due to the deterioration of signal integrity over such length. Building wiring typically connects a central computer to a plurality of remotely located user terminals and is routed between the central computer and the various user terminals by placing it in locations such as in the walls or ceiling of a building.
In general, all of the twisted-pair wires used in building wiring are bundled together and surrounded by a cover thereby forming a substantially round cable. Since all of the twisted-pairs of wires are arbitrarily collected or bundled together, each of the individual wires achieves a random orientation between the point of origin and the point of termination. When the distal end of the cable is terminated, the individual wire conductors are disoriented with respect to their position at the point of origin and accordingly must be manipulated into an ordered sequence as prescribed by the terminating connector used. In addition, the individual wires comprising the twisted-pair cable are typically solid for improved transmission of information over long distances. The flexibility found in stranded wire is unnecessary since building wire is not exposed to as much strain or stress.
In contrast, when a cable is used in an external office space and the length of the transmission line is relatively short, the wire conductors comprising the transmission cable are placed in flat wire. In this arrangement, the individual wire conductors remain ordered within the flat housing at any point along the length of the cable between the point of origin and the point of termination. In addition, the wire conductors used in flat cable for connecting data equipment are typically stranded to reduce fatigue from constant movement.
Known building wiring distribution systems have concentrated bundles of twisted-pair wires to carry signals from a central computer through the walls or ceiling of a building to a wall faceplate. For example, twenty-five pairs of wires are frequently bundled together and surrounded by a protective covering or sheath to form a single trunk cable of building wiring. The signals transmitted over building wiring can originate from virtually any source for example, computer mainframes, minicomputers, data storage systems or other data units. Typically, this active equipment is located a substantial distance from the point of termination such as across a large room or on a different floor of a building. The point of termination is usually a wall panel or faceplate which receives the building wiring and permits connection of external data equipment such as individual user terminals to the building wiring. Flat cable typically links such external data equipment to the point of termination at the wall panel.
In actual practice, a specified wallplate is not directly connected by building wire to a central or mainframe computer but rather the building wire is terminated and reconnected at various intermediate patch panels or punch blocks. Each one of these intermediate points at which the building wire is terminated and reconnected is referred to as a layer of connection. The patch panel is connected to the mainframe computer by building wiring and provides a point of distribution for signals carried by the building wiring from the mainframe computer. Punch blocks consolidate wires from individual wallplates so that these individual wires can be connected to the patch panel by a trunk cable.
Patch panels have connection points comprising fixed numbers of certain types of hardwired connectors which are not easily changed. These connectors are dedicated to a specific type of mating connector or wiring configuration. The type of mating connector suitable for these connectors is predetermined according to the construction of the patch panel. Accordingly, if all the connectors are being used or if a different type of connector is required, an entirely new prewired patch panel must be installed to provide appropriate connectors or alternatively extensive rewiring of the patch panel is required.
The front side of the patch panel has connectors for accessing building wiring carrying information from the mainframe computer. Other connectors access building wiring carrying information ultimately to wallplates. Patch cords are used to connect between these individual connectors to make a final connection between the computer and the wallplates.
The back of the patch panel is configured to accept connectors which terminate a plurality of twisted pair wires of building wiring. Some of these connectors terminate building wiring which is carrying information from a mainframe computer to the patch panel. Other connectors terminate building wiring which is carrying information from the patch panel to punch blocks and ultimately to wallplates.
Building wiring used for sending information to user terminals from the back of a patch panel typically terminates at a punch block. The punch block concentrates all the terminated wires into a single connector which usually contains thirty-six pins for terminating thirty-six wires or fifty pins for terminating fifty wires. These individual wires are punched to the punch block, which makes rewiring difficult. Individual wallplates are connected to this punch block with cables containing a smaller number of wires.
A typical sequence of cables and connections from a mainframe computer to a user terminal begins at the computer. A first building wire trunk cable having a thirty-six pin or fifty pin connector on both ends of the trunk cable connects the computer to the back of a patch panel. Patch cords used on the front of the patch panel appropriately connect building wires of the first trunk cable to a second trunk cable. The second building wire trunk cable connects the back of the patch panel to a punch block. At the punch block, individual connections are made from one end of the second trunk cable to individual wallplates thereby linking a selected output of the computer to a selected wall plate.
Whenever existing building wiring distribution systems are reconfigured, specified individual wires are separated from the other wires of the trunk cable and are grouped together. An additional connector is used to terminate and reroute this group of wires. Because the additional connector creates a new point of connection, an additional punch block or an additional printed circuit (PC) board with an appropriate mating connector is necessary to interconnect the rerouted group of wires with other points of connection further downstream within the wiring distribution system. In some cases, the original punch block contains unused connection points so that the punch block can be stripped down, and the group of wires can be reinstalled at increased time, cost and complication.
Other types of building wiring systems use multiple layers of connection panels with hardwired modular components. In known jack panel mounting systems, a modular plug snaps into a board-mounted modular jack held in place at a point of termination at a wall panel. This forms a first layer of connection. The board typically has 16 board-mounted modular jacks, with eight of the modular jacks hardwired to a first thirty-six pin connector on the back of the board.
The first thirty-six pin connector connects a thirty-six wire building cable to a second thirty-six pin connector which is attached to a second set of eight board mounted modular jacks held by a second jack panel. A third jack panel holds another eight board mounted modular jacks having a thirty-six pin connector at the back. This thirty-six pin connector is connected to the computer by another thirty-six wire cable. Patch cable connected between selected modular jacks of the second jack panel and selected modular jacks of the third patch panel connects the central computer outputs to specified termination points. This arrangement requires at least three layers of jack panels or intermediate points of inter-connection.
In known modular wiring distribution systems, modular jack connectors typically terminate twisted-pair building cable at a point of termination such as a wall plate to permit connection to external data devices. Each modular jack includes a portion defining a complementary cavity formed within a side wall of the modular jack. A modular plug terminating the flat cable fits within the complementary cavity to form the electrical interconnection. In this way, data communication is provided to and between different data units.
Although widely used as a data carrying media, the installation and maintenance requirements of known modular building wiring systems have posed practical difficulties. Principal among these difficulties is the interconnection between two twisted-pair cables. Such difficulties also arise in a twisted-pair cable to flat cable interconnection. In general, office spaces which have changing equipment configurations frequently encounter these problems.
Known twisted-pair modular connectors couple the conducting wire ends of the twisted pair cable to the connector. Methods for terminating twisted-pair cable within jack assemblies utilize an insulation displacement contact termination. The individual wires comprising the cable are sequentially placed on respective fork or barrel terminals of the jack assembly and thereafter punched or pressed into the jack assembly, one at a time, using a specialized tool. The conducting portions of the individual wires are brought into actual contact with complementary contacting portions within the connector. With this mode of connection, it is necessary to manipulate and capture the individual wire conductors at a closely controlled location, because positioning of the conductor has a critical impact on the desired efficiency of the electrical interconnection. Accordingly, such connectors tend to require an inordinate time to align and thereafter insert individual wires of the cable with respective receiving portions of the connector. Further, such connectors tend to misalign upon the application of rotational, longitudinal, or lateral forces.
Known methods for terminating twisted-pair cable with modular plug assemblies are quite similar or the same as methods for terminating flat cable. Such methods employ a crimping technique wherein a relatively small portion of the outer covering layer is removed from the distal end of the cable. Thereafter, the wires are ordered and placed within the plug assembly by hand. The covering layer is likewise placed within the plug connector assembly and is grasped therein when the crimp operation is completed to provide strain relief for the cable. Such methods are suitable for flat cable, where the individual exposed wires remain ordered after removal of a small portion of the covering layer. However, building wiring poses the additional practical problem of manipulating and ordering the individual wires with only small portions of the wire exposed.
Still further problems in known building wire systems frequently arise when the system is reconfigured or equipment upgraded or changed. For example, when interconnections are changed at a terminal location such as a wallplate, the existing jack assembly terminating the twisted-pair cable is routinely replaced with a new modular jack assembly. However, the twisted-pair cable must again be terminated with the new modular jack assembly. Moreover, any system reconfiguration using this method of termination requires a significant amount of installation time.
Twisted-pair modular connectors in general are susceptible to longitudinal forces on the conducting portions of the twisted-pair cable. Retention of the individual wire conductors forming the interconnection is therefore another frequent problem. Each wire conductor must be secured to prevent relative movement of the wire and mating connector since virtually any movement adversely effects the quality of the interconnection. The physical attachment of the cable, however, must avoid the application of undue stress on the cable or the individual wire conductors which causes eventual breakage of the wire conductors due to stress fatigue.
Accordingly, known types of building wiring systems and connectors, while performing satisfactorily under certain circumstances, are overly complex and difficult to install, maintain and modify. The assembly and maintenance of multiple layers having complex mechanical parts associated with such systems involve considerable wasted effort owing to installation of intermediate layers of interconnection. The connectors used require alignment of the individual wire conductors within the connector and completing the mechanical termination of the cable. Moreover, known methods and devices for termination are quite time consuming and labor intensive because each wire is handled and terminated individually. In addition, a relatively high level of training is required to determine appropriate routing of the building cable and field termination of the distribution components.